The objective of this program is to train physician-scientists in basic biomedical research, with an emphasis on the pathogenesis of infectious diseases. The focus will be on diseases of worldwide importance, in particular, leishmaniasis and HIV infection. The training program will utilize the resources of Cornell University Medical College (W. Johnson, E. Cesarman, J. Ho, C. Nathan), the Rockefeller University (D. Ho, R. Steinman), and the Aaron Diamond AIDS Research Center (D. Ho). The program faculty are all physicians and funded scientists, committed to research on HIV and its major opportunistic infections. The training faculty has a long history of successful collaboration in research and training of international biomedical scientists through NIH Fogarty programs and will now apply that experience to the training of US physician-scientists. The program will recruit US physicians who have completed their clinical training (medicine, pediatrics, pathology) and are seeking academic investigative careers. The training faculty share the view that the physician-scientist is truly an endangered species. This training grant will provide young physicians with an opportunity to make the transition from their clinical training to the laboratory. The research training will be for 2-3 years with four fellows in each year. Trainees will have the opportunity to work with outstanding mentors in Haiti (Pape) and in Brazil (Carvalho and Lapa e Silva), if it is relevant to the US laboratory research. The research in Haiti and Brazil is focused on HIV natural history and transmission studies, opportunistic infections (leishmaniasis, tuberculosis, epidemiology, immunopathology, and interventions (behavioral, drug, vaccine).